Color-sensitive photographic emulsion and process of making same.



UNITED STATES Patented March 21, 1905.

PATENT OFFICE.

KARL KIESER, OF ELBERFELD, GERMANY, ASSIGNOR TO FARBENFAB- RIKEN OFELBERFELD 00., OF NEW YORK, N. Y'., A CORPORATION OF NEW YORK.

COLOR-SENSITIVE PHOTOGRAPHIC EMULSION AND PROCESS OF MAKING SAME.

SPECIFICATION forming part of Letters Patent No. 785,219, dated March21, 1905.

Application filed October 30,1903. Serial No. 179,183.

To all whom it may concern.-

Be it known that I, KARL KIEsER, doctor of philosophy, chemist, residingat Elberfeld, Germany, (assignor to the FARBENFABRIKEN or ELBERFELD 00.,of New York,) have invented a new and useful Improvementin Oolor-Sensitive Photographic Emulsions and Processes of Making Same; and I dohereby declare the following to be an exact and clear description of myinvention.

I have found a new and valuable process for preparing color-sensitivephotographic emulsions, being of great technical value for themanufacture of plates, papers, films, or the like.

My new process consists in first treating silver salts sensitive tolight with a suitable sensiti zing-dyestuff or a mixture of suchdyestuffs and then preparing the photographic emulsions with the aid ofthe so-dyed silver compounds. The emulsions thus prepared possess a highdegree of sensitiveness.

On employing my process a suppression of the effect of one -or ofseveral dyestuffs by another dyestutf being present at the time isavoided. The number of sensitizing-dyestuffs which can be employed formy process is therefore much increased, and it is possible to attaincomplete isochromatisme. One can employ dyestuffs being only soluble insolvents which cannot be mixed withthe emulsions or which cannot diffuseinto the substratum. In my new process one can use higher concentratedsolutions of sensitizingdyestuffs than is possible in other processes,and one can so obtain a higher degree of sensitiveness.

In carrying out my new process practically I can proceed as follows: Inorder to prepare the gelatin emulsion, I proceed in the wellknown mannerby introducing an aqueous solution of silver nitrate (one molecule) intoan aqueous solution of hydrobromic acid (one molecule) while stirring.The silver bromid thus precipitated in a pure and granulated state isthen washed with water and shaken for five minutes with a solution of asensitizing-dyestuif, (about one per ten thousand.) The colored silversalt thus obtained is washed until the wash-water is uncolored-andintroduced into a four-per-cent. solution of gelatin at L centigrade. Itis stirred for several hours until the emulsion is homogeneous, and thisemulsion is then employed for coating glass plates, papers, celluloidplates, and the like. It will also be possible to employ other sensitivesilver salts and other emulsifying agentsfor example,collodion. On usingthis substance it is necessary to precipitate the silver salts fromalcoholic solutions.

The plates, papers, films, or the like are coated with the aboveemulsionin the 'usual manner.

Having now described my invention and in what manner the same isperformed, what I claim as new, and desire to secure by Letters Patent,is

1. In the art of producing color-sensitive photographic emulsions theprocess which consists in first treating silver compounds sensitive tolight with suitable sensitizing-dyestufls and then emulsifying theso-dyed products, substantially as described.

2. The herein-described color-sensitive photographic materials which, asthe spectroscopic test shows, contain colored grains of silver salt,while the emulsifying agent itself remains uncolored, substantially asdescribed.

In testimony whereof I have signed my name in the presence of twosubscribing witnesses.

KARL KIESER.

Witnesses:

Or'ro KoNIe, JosEPH LANGE.

